Present day internal combustion engines, such as the typical automotive engine, require that a fuel/air mixture be delivered to each of the combustion chambers to subsequently be ignited for the extraction of energy to produce the work of the engine. Creating a fuel/air mixture having the proper proportions to provide clean and efficient burning of the fuel has been the purpose of fuel delivery systems in the prior art. The conventional carburetor attempts to provide the appropriate fuel/air mixture throughout a broad range of engine operation by metering liquid fuel into an air stream; elaborate techniques have been employed to achieve the correct fuel/air mixture throughout a broad range of engine operation. However, the liquid fuel is seldom completely vaporized in the ideal proportions and the resulting fuel/air mixture is poorly controlled, poorly distributed, and very inefficiently utilized.
In an attempt to more accurately control the fuel/air mixture to meet the varying demands of the engine during operation, fuel injection systems have been employed for directing a measured spray or atomized quantity of liquid fuel into an air stream to be mixed with the air to provide a fuel/air mixture for combustion. Such atomizers or fuel injectors have been placed in the same position as conventional carburetors (throttle body injection) or more efficiently have been distributed along the intake manifold with an injector located at an appropriate position adjacent each inlet of the respective cylinders. With the advent of more sophisticated electronic controls, it has been possible to more accurately control the operation of these fuel injectors for the measurement of the correct amount of liquid fuel to be injected into the air stream to provide a proper fuel/air mixture. Numerous engine operational parameters can be sensed and converted into appropriate electrical signals for application through a computerized system to electrically energize the respective fuel injectors at the appropriate time and duration.
All of the above prior art systems depend upon the introduction of liquid fuel into an air stream. The fuel/air mixture that is required for proper combustion is a mixture of air and fuel vapor; therefore, for ideal mixing, fuel vapor, and not liquid fuel, should be the constituent to be mixed with the air. Incomplete or uneven vaporization of fuel causing variations in the mixture ratio or imbalances in the mixture delivered to different cylinders greatly reduces the efficiency of the overall engine system. Further, improper fuel/air mixtures or improper control of the mixture and deviation of the mixture from ideal is a major contributor to atmospheric polluting combustion products.
Prior art fuel supply systems also include techniques for vaporizing the liquid fuel prior to combining the fuel with air. Such systems are generally known as vapor carburetors and usually provide a means for heating the liquid fuel to a vapor state before providing the vaporized fuel to a mixing device such as a carburetor to provide an appropriate fuel/air mixture. Such prior art vapor carburetors have not been able to provide a means for controlling the vaporization of the liquid fuel so as to insure complete vaporization while supplying and controlling the quantity of vapor provided to the fuel/air mixing device.